Postencephalitic Parkinsonism (PEP)

Infectious diseases

General outline

PEP is a progressive neuro-degenerative disease with clinical features referable mainly to the extrapyramidal and oculomotor systems and cognitive deterioration. It represents a chronic complication of encephalitis lethargica (EL) or Economo’s encephalitis or sleep sickness that emerged during and after World War I.

Neuropathology: multisystem neuronal degeneration and cell loss, with gliosisin many brainstem nuclei, in particular substantia nigra, locus ceruleus, and others with globous neurofibrillary tangles in residual neurons in many subcortical nuclei. Cortical pathology is common with frequent NFTs in hippocampus, entorhinal, frontal and insular cortices, differing in distribution from those in AD.

Caregiver problems

Similar to those in Parkinson’s disease and its late complications.

Causes and risk factors

The causes and risk factors are unknown. Recent microbiological methods were unable to demonstrate any virus, in particular, wild-type influenza virus, that caused influenza pandemic in 1918-21, simultaneously to LE, could not be detected in brain material of PEP patients. Relationship between EL/PEP and influenzy remains enigmatic.

Frequency

Frequency currently extremely rare; since 1970 only single cases reportedMain occurrence of EL between 1918 and 1924. Between 1925-38, PEP reporesented almost 50% of all cases of parkinsonism diagnosed at that time. Later on, incidence of PEP ranged from 4 - 30% (mean of 13%) of all cases of parkinsonism. In recent years, incidence of PEP in austopsy series dropped from 6% (1957-70) to almost zero in last decade.

Diagnostic procedures

Similar to Parkinson disease (PD), but history of EL necessary. No diagnostic test available.Diff. diagnosis: mainly against PD, but significant differences: 1. onset of symptoms in younger age, including children and adults aged 25-40 yrs; 2. rare occurence of rest tremor; 3. progression of disease in discontinous spurts; 44. prior history of acute EL.

Care and treatment

Similar to PD. Patients may variably respond to L-dopa therapy. Late complications to be treated like those in PD.

Ongoing research/Clinical trials

Trials to identify causing viral agent using modern molecular biologic and genetic methods. Due to almost total extinction of PEP, repository archival material represents the only source for modern investigations, that up to the present, failed to identify a causaive or transmissible agent.

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Acknowledgements

This information was gathered in the framework of the European Commission financed project "Rare forms of dementia". Neither the European Commission nor any person acting on its behalf is responsible for any use that might be made of the following information.